The present invention relates to engine block heaters, and more particularly, to a combination of a core plug and block heater with a removable, free rotating heating element cartridge.
Engine block heaters are well-known in the prior art, and are generally of two types. An immersion-type block heater includes a heating element inserted through an engine bore such that the heating element is xe2x80x9cimmersedxe2x80x9d into an engine coolant or fluid. Upon an electrical connection to the heating element, heat from the element warms the engine fluid directly, permitting improved starting of the engine in extreme cold. The heating element is typically placed within an open-ended housing, which is threadedly inserted into the engine bore, providing a direct access channel for the heating element to contact the fluid. To prevent fluid leakage between the heating element and the housing, the heating element is permanently welded or soldered into the housing. Because the heating element is permanently fixed within the housing, replacement of the heating element requires replacement of the entire heater and drainage of the fluid.
Alternatively, a housing, with the permanently fixed heating element extending therein, is inserted into the engine bore through an O-ring sealer, mounting the O-ring between the housing and the interior walls of the bore. The O-ring is designed as a seal to prevent fluid from escaping through the bore around the loose interface formed between the surface walls of the housing and the bore. In this heater configuration, a fastener secures the housing, inserted through the O-ring, in a fixed position to an exterior surface of the engine block. The housing, and correspondingly the heating element, do not rotate within the bore because such rotation may distort the O-ring sealer, opening gaps between the housing and bore surfaces from which fluid may leak.
To install or replace an immersion heater, all engine fluid must be drained, and in some cases, if used, the O-ring must be replaced. Further, the use of O-ring, over a period of time under high temperatures, results in an addition disadvantage for the O-ring may permanently set to the bore, or otherwise deteriorate, thereby failing to provide a sufficient seal and allowing engine fluid to leak through the bore and soil the electrical connection between the heating element and an external power source causing the heater to malfunction. Likewise, the O-ring may fail to seat properly during installation, causing an insufficient seal leading to the loss of engine fluid. Additionally, aftermarket installation of an immersion-heater is cumbersome and time consuming, requiring drainage of the engine fluid before the heater may be installed or the heater and/or the heating element replaced.
A second type of engine block heater is referred to as a xe2x80x9cdryxe2x80x9d or xe2x80x9ccartridge-typexe2x80x9d heater. Instead of being inserted through a bore that taps an engine fluid chamber, the dry heater is threadedly inserted into a bore specially drilled into a portion of the engine housing adjacent to but not intersecting the fluid chamber. Alternatively, the heater is placed in the bore by a fastener that mounts the heater in a fixed position to an external surface of the engine block. In either application, the heater, within the bore, does not directly contact the coolant. When an electrical connection is made to the dry heater, heat is conducted directly into the walls of the engine, and from there, indirectly to the engine coolant. While the dry heater eliminates engine fluid leaks, its effectiveness and efficiency is reduced because of the relatively large thermal mass (i.e. the engine block and/or head) that must be heated prior to heating the fluid within the engine.
In both types of heaters, electrical power is provided to the heating element by means of a power cord/connector combination that engages the heating element. One part of the connector combination is usually permanently mounted to the heating element. As may be appreciated, the final orientation of the heater-mounted connector portion is highly dependent upon the rotational orientation of the heating element after threaded interconnection to the engine block. In particular, thread start and stop points may vary significantly between engines, and even between engines of the same type due to manufacturing variances. Thus, a final heater-mounted connector orientation may vary significantly between identical engines. Moreover, the cord-mounted connector portion has limited positions in the confined space about the engine to effect interconnection between the cord and the heating element, thereby increasing the difficulty of connecting the heater to a power supply for operation.
Accordingly, an engine block heater is needed that overcomes the aforementioned difficulties and limitations.
To overcome the difficulties associated with block heaters, the present invention provides a generally annular cylindrical core plug having one open axial end and one closed axial end to define a hollow housing. A portion of the housing exterior is threaded for engagement with a corresponding threaded core bore of an engine that extends from an outer surface of the engine to an interior fluid chamber. Additionally, the housing exterior may include a sealing flange for sealingly engaging the outside perimeter of the engine core bore.
During installation, the closed end of the housing is inserted into the bore, and the housing is threadedly secured in place such that at least a portion of housing projects inwardly of the bore and is immersed in engine fluid inside the chamber. At any time after installation of the housing, a heating element is inserted into a housing cavity. The heating element has a radial diameter slightly smaller than the radial inner diameter of the housing cavity for easy insertion and rotation therein. Once inserted, a quick-release fastener is installed to retain the heating element within the housing while still allowing free rotation of the heating element.
The heating element of the present invention is therefore dry inserted within the housing so that no direct contact exists between the heating element and the engine fluid. As a result, the heating element does not need to be permanently welded into the housing or no O-ring is required to seal the interface between the surfaces of the bore and the housing, thereby removing the possibility of leaks therebetween. If desired, a flange may be formed on the exterior of the housing adjacent the threaded portion to tightly fit against the outer surface of the engine, thereby sealing the bore against leakage.
Additionally, since the heating element is retained within the housing only by the quick-release fastener, the heating element is free to rotate 360 degrees within the housing. Any electrical connector attached to the heating element is likewise free to rotate, making orientation of the electrical connector from the external power source easier, especially within confined spaces. The free rotation of the heating element allows the electrical connector to interconnect with the heating element completely independently of the final orientation of the heating element inside the core plug or the end orientation of the core plug within the engine bore. Upon application of electrical current, the heating element heats, thermally expanding the materials that constitute the heating element. This thermal expansion increases the diameter of the heating element, forcing the exterior walls of the heating element against the internal walls of the housing cavity to lock the heating element in place within the housing and to provide a direct transfer path of heat conductance from the heating element to the housing to be radiated directly to the engine fluid and the engine block. The present invention therefore has the advantages of an immersion heater, namely the ability to directly warm the engine fluid to quickly and efficiently heat the engine, and a dry heater, which provides simplified installation and replacement of the heater while minimizing the possibility of fluid leakage.